1. Field of the Invention
The present invention relates to an image processing apparatus, and more particularly to such image processing apparatus capable of extracting a particular image area and a process therefor.
2. Related Background Art
For the purpose of image synthesis, it is necessary to extract particular image areas from various images. The extracted image area will be hereinafter called the object area, and the remaining area will be called the background area. A conventional method consists of cutting out the object area with a cutter, or painting the background area with a brush; and such operation requires considerable skill as well as significant time and labor. However, such drawbacks are prevented by a recently developed apparatus in which an image area extraction can be achieved on a display, for example, with a digitizer or the like. Such apparatus is advantageous in that the extraction can be made on an enlarged display image and that an error in operation can be easily corrected, but delicate and precise extraction still requires skill and labor.
Therefore, for automating such image extraction there have been proposed a method of extracting the edge of an object area, and a method of extracting an object area by the uniformity of three primary colors, red, green and blue. The former edge extraction method consists of conducting an edge enhancement, and painting uniformly the interior of the thus obtained edge line. However, such painting step is sometimes difficult because the edge line does not necessarily define a closed area. Also, there remains a problem of how to treat the unnecessary edge line formed for example by a noise component in the image. The latter, three primary color method extracts the object area by reading the three primary color values of a pixel and by judging whether said values are close to those of a neighboring pixel. However, this method does not allow approximate extraction of the object area since the three primary color values vary considerably, even for the skin color of a human face, for example between the nose in the sunlight and the forehead shadowed by the hair.